Arid lands in the Sudan have been subjected to degradation manifested by loss of soil fertility, shortages of fodder and fuel, and moving sands. Acacia tortilis, A. senegal and Prosopis chilensis are valuable afforestation species to restore these lands and provide fodder, fuelwood and other products. Animals, particularly goats and sheep, are effective long-distance dispersers of seeds. The ingested seeds are preserved from further attacks of predators and their germination capabilities are enhanced by ingestion and pelleting. Because of the small mass of the droppings, the ingested seeds are transported by wind and water to low-lying places where run-off water usually collects.